مجله علوم و مهندسی زلزله
پیاپی 1 (زمستان 1393)

There are a few methods for seismic vulnerability assessment of bridge structural systems. The development of vulnerability information in the form of fragility curves is an approach when the information is to be developed accounting for a multitude of uncertain sources involved، such as، structural characteristics، estimation of seismic hazard and site condition. Inherent randomness is involved to these uncertain factors. The major effort of this study is placed on the development of empirical fragility functions by utilizing the damage data from past earthquakes considering composite inherent randomness of the uncertain factors. The introduced procedure is suitable for the development of fragility curves under the assumption that they can be presented by two-parameter lognormal distributions. The empirical fragility curves are developed using 768 bridge damage data obtained from the 1994 Northridge and the 1995 Kobe earthquakes، which could be used as reference curves for seismic risk assessment studies of the similar bridges in Iran.

Near-fault seismic events have been popular research topics in earthquake engineering, especially, in last two decades. A variety of research programs have been conducted to characterize the unique nature of near-fault events from both structural and seismological point of views. In this paper, after the introduction of S-Transform as a modern timefrequency representation which can measure local characteristics of a signal such as amplitude, frequency, and phase at any time instant, a new robust filtering method is proposed and applied to extract the pulse-like part of nearfault ground motion records. Seven pulse-like near-fault recorded ground motions have been selected from literature such that the comparison of results with similar available methods can be possible. After the extraction of pulse-like parts, the nonlinear dynamic behavior of two 3-D reinforced concrete moment frames with 6 and 9 stories is studied by using Incremental Dynamic Analysis (IDA) under support excitation by original ground motions, extracted pulses and residual ground motions. To investigate the sensitivity of results to the pulse period, two extra steel moment frames with 3 and 12 stories are modeled. The results deeply questions the reliability of the application of low-frequency extracted pulses as the representative of original ground motions in dynamic time history analysis, especially, when the nonlinear behavior is considered.

Nowadays, the use of zonation maps such as ground type zonation, geotechnical parameters, seismic hazard intensity as well as landslides zonation maps have been deployed. These maps are prepared with regard to special purposes and are based on widespread data banks and existing standards. Using these maps, projects costs can be decreased and decision making speed in engineering judgments will increase. In this paper, a new empirical relation is recommended between dynamic probing tests results and shear wave velocity using geotechnical data and dynamic probing tests data related to different sites and the results of down hole tests in 10 different locations in Qom plateau.

In this study, by using analytical methods, new formulas for calculating natural frequencies of retaining walls with variable cross section are proposed. Different methods for calculating natural frequency, such as analytical, numerical and experimental methods, are described. Then, using the exact solution of the problem, new formula for calculating the first mode of vibration in retaining walls with constant cross sections is proposed. The Rayleigh approximation method was used to obtain the natural frequency of retaining walls with varying cross sections and taking the effect of backfill soil into the consideration. The results obtained from the proposed formulas are compared with the result of numerical analysis using finite element software and good agreements have been found.

Seismic energy is scattered in the form of seismic waves from the underground source to the surficial structures.These waves are known as body waves and will generate volumetric deformations by compressional waves and distortional deformations generated by rotational or shear waves. However, the body waves will generate other deformations at the interface of layers or the ground surface due to specific boundary conditions. Boundary conditions corresponding to the free surface allow additional answers to the equations of motion be obtained. Since the earthquake engineering examines effects of seismic waves on the structures which are in or near ground surface and because surface waves are attenuated slower than body waves with distance, the surface waves are more important. Problem of wave propagation in saturated porous media was discussed first by Biot in the mid-twentieth century, after the formulation of the theory of saturated porous medium.Extension of the theory of elastic wave propagation in unsaturated soils which are made of a solid porous skeleton that the empty space is filled with water and air, founded the basis for solving the most complex problems of waves propagation in unsaturated soils. It was found that three compression waves (P1, P2 and P3) and a shear wave propagate in unsaturated porous media. Furthermore, Rayleigh wave are identified as the superposition of P and Swaves at the free surface. This results in propagation of three Rayleigh waves (R1, R2 and R3) at the free surface. The purpose of this research is to obtain the Rayleigh wave characteristics and the governing equations, according to the compression and shear waves. The theoretical results are demonstrated through some examples at the end.

In this article, we showed the results of pattern recognition by using numerical simulations models using Copula methods for earthquake prediction for central Alborz (Tehran region) and compared them with the results of seismogenic nodes. The goal of this paper is to identify where earthquakes with M>6.0 can occur and define the assemblage of geological-geomorphological features that discriminate such sites from areas of lower seismic potential. It is demonstrated that the synthetic clustering in space and time of earthquakes are useful for seismic hazard assessment and intermediaterange earthquake in Tehran region. In these experiments, we will present a Copula methods that can finds the unknown location of the possibility major earthquakes by using foreshocks, Seismic silence, and Doughnut pattern in this region. Our model and computer simulations obtain these synchrony results across in Tehran region located in center of Alborz in Irananian plate.